Diolefins with an ether/thioether functionality as ligands in the coordination sphere of Ni and Rh

A diolefin ether, trop₂O (2), and a diolefin thioether, trop₂S (3), have been investigated as ligand analogues of the well-established diolefin amine, trop₂NH (1). Compounds 2 and 3 form different conformers in solution and in the solid state. Whereas 2 could be coordinated to Ni(0), 3 was found to be more suited for coordination to Rh(i). The coordination chemistry, electrochemical properties, and ligand exchange phenomena of the resulting complexes, [Ni(trop₂O)(PPh₃)] (5) and [Rh(trop₂S)(L)_n][OTf] (6: L = NCMe, n = 2; 7: L = 2,2′-bipy, n = 1) were investigated by analytical techniques including NMR spectroscopy, single crystal X-ray analysis, and cyclic voltammetry. The results were compared with those obtained for the amine analogues of 5, 6, and 7.